RSLogix 500 24 hour cycle logic

Hello

It is probably very simple question but what is the best way to go about altering two blowers every 24 hours?
In my logic same blower will come on sunday and monday and it is not right

Thank you

Try this instead of your first 2 rungs. It will alternate your two bits at midnight.

Re: bernie_carlton

Thank you for the sample but I can not seem to make it work on ML1400. it does not switch

Thank you for the sample but I can not seem to make it work on ML1400. it does not switch

Click to expand...

Post your code (.RSS file)and someone will take a look.

Make sure that B3:0/0 and B3:0/1 are not used elsewhere in your code. I just picked those two as examples. The other two bits were from your posted code.

Hello
I have attached updated code. I changed HR to seconds to see how it would work. It does not change every 60 seconds. Always stays on Rung 2, B3:4.9 EN

Thank you

Everything works fine. I have overlooked a reference somewhere else in the code

Thank you for your help

RE: bernie_carlton

I am trying to implement 3 pump 24 hour solution. Only two pumps at any given time should be running and they would alternate every 24 hours. Can not seem to get the logic right, should I be using two OSRs?
Thank you

Increment a counter every 24 hours using the logic Bernie provided. Set the preset to 3, on the next rung if the counter is DoNe, RESet it.

When the .acc = 0, run pumps 1,2
When the .acc = 1, run pumps 2,3
When the .acc = 2, run pumps 1,3

Hot dog, now we are getting down to it!
Now, if one pump fails and you need to pull it out of the rotation ???

As Alaric has pointed out before, if you run them equal times with equal loads, then they will all fail at about the same time. So now instead of one main pump worn out and needing replacing (while you keep running the other two), you got to shut down and replace all three!

Actually, equal time may not cause them to fail at the exact same time, but in the same fiscal year. The company accountants may not want to wreck the maintenance budget by allocating money for 3 pumps the same year, so....

They don't teach the financial part in PLC school, but just how to run the motors evenly.

In the real world of high company finance:
1st Year, you would buy Pumps 1 and 2 and run evenly, taking a tax break for capital depreciation for 2 pumps.
2nd Year, buy Pump 3 and run Pumps 1 and 3 evenly, taking a tax break for capital depreciation for 3 pumps.
3rd Year, run Pumps 1 and 2 evenly, taking a tax break for capital depreciation for 3 pumps.
4th Year, run all 3 Pumps evenly, taking a tax break for capital depreciation for 3 pumps.
....
Run until Pump 1 fails (most wear), replace it and continue even rotation.
...
Run until Pump 2 fails (next most wear), replace it and continue even rotation
....
Run until Pump 3 fails, replace it, and continue even rotation.
...
Repeat cycle.

Hopefully, the pumps will fail in different years, allowing the accounts time to recover from the shock. But you got Murphy's Law to contend with, so Pump 3 might actually fail first!

In years with sympathic tax laws, you may get Accelerated Depreciation, which makes buying new equipment effectively cost less. So instead of contiuning to run an old pump, it may be cheaper overall to buy a new one, if you can claim enough Depreciation the first year to pay for it. In years of increasing business taxes (like 2011), you may have to skip the replacement altogether. Our screwed-up convoluted tax code is one reason businesses are not expanding.

Now write a program for the above!

I agree with Lanice on this for the purpose of trying to maintain even wear.

On the other hand there are good reasons to rotate pumps, like to prevent sludge or other material from caking up in them, or rusting out the bearings, by sitting idle for weeks...

As for dealing with taking one of them out of the rotation, that is likely going to be an issue. To do that, the basic premise is the same, but the outputs become indirect. "Run Pump 1 and Pump 2" then has to be programmed to mean "Run the pumps presently assigned to positions 1 and 2".

Re: OkiePC

Per your suggestion I have added a counter. Looks like I go wrong about it since last Rung wins and pumps do not come on as they should. Please ignore everything pass rung 8

Thank you for your help

Let me rephrase:

Run pump 1 when the .acc = 0 or 2
Run pump 2 when the .acc = 0 or 1
Run pump 3 when the .acc = 1 or 2

One OTE per pump output address...

Bearsgone,

Instead of putting two OTE in parallel on your rungs, use one OTE (B3:4/8, B3:4/9, and B3:4/10 only used for 1 OTE each), but put two EQU statements in parallel at the input side of Rungs 2, 3, and 4, each with one of the comparisons to be made for each pump.

If you make the above change, then you will need to change Rungs 9 and 10 also (removing the left-side parallel branches, leaving only one B3:4 input for A on Rung 9, and one for B on Rung 10.

Lancie1: that was an interesting post you made above, post #10 in this thread. I have not seen that stated before. Made me think about the 50-something exhaust fans that will all accumulate the same hours in a program I did last year...

Always learning something when I visit here!